#!/usr/bin/perl -w
use strict;
my $count = 0;
 
open FILE, ">s_5_2_sequence.txt";
while (<>) {
  my $line = $_;
  if($line =~ /^@/) { $count++}
  elsif ($line =~ /N+/) {next}
  last if $count == 1000;
  print FILE $line;
}
close FILE; 
